Overmolded polyamide composite structures and processes for their preparation

ABSTRACT

Disclosed herein are overmolded polyamide composites structures and processes for their preparation. The disclosed overmolded composite structures comprise i) a first component having a surface, at least a portion of which is made of a surface resin composition, selected from polyamide compositions comprising a blend of two or more fully aliphatic polyamides having a melting point of at least 250° C., and comprising a fibrous material being impregnated with a matrix resin composition, ii) a second component comprising an overmolding resin composition, adhered to said first component over at least a portion of the surface of said first component, and wherein the matrix resin composition is selected from polyamide compositions comprising a one or more fully aliphatic polyamides having a melting point of at least 250° C.

CROSS REFERENCE TO RELATED APPLICATIONS

The present application claims the benefit of U.S. ProvisionalApplication No. 61/408,166, filed Oct. 29, 2010, which is now pending,the entire disclosure of which is incorporated herein by reference; andU.S. Provisional Application Nos. 61/410,093, filed Nov. 4, 2010;61/410,100, filed Nov. 4, 2010; 61/410,104, filed Nov. 4, 2010; and61/410,108, filed Nov. 4, 2010, all of which are now pending, the entiredisclosures of which are incorporated herein by reference.

FIELD OF THE INVENTION

The present invention relates to the field of overmolded compositestructures and processes for their preparation, particularly it relatesto the field of polyamide overmolded composite structures.

BACKGROUND OF THE INVENTION

With the aim of replacing metal parts for weight saving and costreduction while having comparable or superior mechanical performance,structures based on composite materials comprising a polymer matrixcontaining a fibrous material have been developed. With this growinginterest, fiber reinforced plastic composite structures have beendesigned because of their excellent physical properties resulting fromthe combination of the fibrous material and the polymer matrix and areused in various end-use applications. Manufacturing techniques have beendeveloped for improving the impregnation of the fibrous material with apolymer matrix to optimize the properties of the composite structure.

In highly demanding applications, such as for example structural partsin automotive and aerospace applications, composite materials aredesired due to a unique combination of lightweight, high strength andtemperature resistance.

High performance composite structures can be obtained usingthermosetting resins or thermoplastic resins as the polymer matrix.Thermoplastic-based composite structures present several advantages overthermoset-based composite structures such as, for example, the fact thatthey can be post-formed or reprocessed by the application of heat andpressure, that a reduced time is needed to make the composite structuresbecause no curing step is required, and their increased potential forrecycling. Indeed, the time consuming chemical reaction of cross-linkingfor thermosetting resins (curing) is not required during the processingof thermoplastics. Among thermoplastic resins, polyamides areparticularly well suited for manufacturing composite structures.Thermoplastic polyamide compositions are desirable for use in a widerange of applications including parts used in automobiles,electrical/electronic parts, household appliances and furniture becauseof their good mechanical properties, heat resistance, impact resistanceand chemical resistance and because they may be conveniently andflexibly molded into a variety of articles of varying degrees ofcomplexity and intricacy.

U.S. Pat. No. 4,255,219 discloses a thermoplastic sheet material usefulin forming composites. The disclosed thermoplastic sheet material ismade of polyamide 6 and a dibasic carboxylic acid or anhydride or estersthereof and at least one reinforcing mat of long glass fibers encasedwithin said layer.

For making integrated composite structures and to increase theperformance of polymers, it is often desired to “overmold” one or moreparts made of a polymer onto a portion or all of the surfaces of acomposite structure so as to surround or encapsulate said surfaces.Overmolding involves shaping, e.g. by injection molding, a secondpolymer part directly onto at least a portion of one or more surfaces ofthe composite structure, to form a two-part composite structure, whereinthe two parts are adhered one to the other at least at one interface.The polymer compositions used to impregnate the fibrous material (i.e.the matrix polymer composition) and the polymer compositions used toovermold the impregnated fibrous material (i.e. the overmolding polymercomposition) are desired to have good adhesion one to the other,extremely good dimensional stability and retain their mechanicalproperties under adverse conditions, including thermal cycling, so thatthe composite structure is protected under operating conditions and thushas an increased lifetime.

Unfortunately, conventional thermoplastic polyamide resin compositionsthat are used to impregnate one or more fibrous layers and to overmoldthe one or more impregnated fibrous layers may show poor adhesionbetween the overmolded polymer and the surface of the componentcomprising the fibrous material, i.e. the composite structure. The pooradhesion may result in the formation of cracks at the interface of theovermolded composite structures leading to reduced mechanicalproperties, premature aging and problems related to delamination anddeterioration of the article upon use and time.

In such case of weak adhesion, the interface between the compositestructure and the overmolding resin will break first, rendering theovermolded composite structure weaker than either of its components.Therefore, high adhesion strength between the components is highlydesirable. However, once the bonding strength is high enough that theinterface can sustain the applied load without being the first to break,yet higher mechanical performance of the structure is highly desirableas is needed for the most highly demanding applications. Lowermechanical performance in these most demanding applications may impairthe durability and safety of the article upon use and time. Flexuralstrength, i.e. the maximum flexural stress sustained by the testspecimen during a bending test, is commonly used as an indication of amaterial's ability to bear (or to sustain, or to support) load whenflexed. When overmolding a resin composition onto at least a portion ofa composite structure, high mechanical performance such as flexuralstrength of the structure is desired beyond that realized by goodbonding strength between the composite structure and the overmoldingresin.

There is a need for an overmolded polyamide composite structure, thatexhibits good mechanical properties, especially flexural strength andhaving at least a portion of its surface allowing a good adhesionbetween its surface and an overmolding resin comprising a polyamideresin, and an overmolded composite structure that exhibits goodmechanical properties made of said composite structure.

SUMMARY OF THE INVENTION

Described herein is an overmolded composite structure comprising: i) afirst component having a surface, which surface has at least a portionmade of a surface resin composition, and comprising a fibrous materialselected from the group consisting of non-woven structures, textiles,fibrous battings and combinations thereof, said fibrous material beingimpregnated with a matrix resin composition, ii) a second componentcomprising an overmolding resin composition, wherein said secondcomponent is adhered to said first component over at least a portion ofthe surface of said first component, and wherein the surface resincomposition wherein the surface resin composition is selected frompolyamide compositions comprising a blend of two or more fully aliphaticpolyamides having a melting point of at least 250° C. and wherein thematrix resin composition is selected from polyamide compositionscomprising a one or more fully aliphatic polyamides having a meltingpoint of at least 250° C. Preferably the surface resin composition isselected from polyamide compositions comprising a blend ofpoly(tetramethylene hexanediamide) (PA46) with one or more fullyaliphatic polyamides having a melting point of at least 250° C. Evenmore preferably, the surface resin composition is selected frompolyamide compositions comprising a blend of poly(tetramethylenehexanediamide) (PA46) with poly(hexamethylene hexanediamide) (PA66).Even more preferably, the surface resin composition and the matrix resincomposition are selected from polyamide compositions comprising a blendof poly(tetramethylene hexanediamide) (PA46) with poly(hexamethylenehexanediamide) (PA66).

Further described herein is a process for making the overmoldedcomposite structure described above. The process for making theovermolding composite structure described above comprises a step ofovermolding a second component comprising an overmolding resincomposition on the first component described above.

DETAILED DESCRIPTION

The overmolded composite structure according to the present inventionhas improved impact resistance and flexural strength and shows goodadhesion when a part made of an overmolding resin composition comprisinga thermoplastic polyamide is adhered onto at least a portion of thesurface of the composite structure. A good impact resistance andflexural strength of the overmolded composite structure and a goodadhesion between the composite structure and the overmolding resin leadsto structures exhibiting good resistance to deterioration and resistanceto delamination of the structure with use and time.

Several patents and publications are cited in this description. Theentire disclosure of each of these patents and publications isincorporated herein by reference.

As used herein, the term “a” refers to one as well as to at least oneand is not an article that necessarily limits its referent noun to thesingular.

As used herein, the terms “about” and “at or about” are intended to meanthat the amount or value in question may be the value designated or someother value about the same. The phrase is intended to convey thatsimilar values promote equivalent results or effects according to theinvention.

As used herein, the term “melting point” in reference to a polyamiderefers to the melting point of the pure resin as determined withdifferential scanning calorimetry (DSC) at a scan rate of 10° C./min inthe first heating scan, wherein the melting point is taken at themaximum of the endothermic peak. In customary measurements of meltingbehavior of blends of polymers, more than one heating scans may beperformed on a single specimen, and the second and/or later scans mayshow a different melting behavior from the first scan. This differentmelting behavior may be observed as a shift in temperature of themaximum of the endothermic peak and/or as a broadening of the meltingpeak with possibly more than one peaks, which may be an effect ofpossible transamidation in the case of more than one polyamides.However, when selecting polyamides in the scope of the currentinvention, always the peak of the melting endotherm of the first heatingscan of the single polyamide is used. As used herein, a scan rate is anincrease of temperature per unit time. Sufficient energy must besupplied to maintain a constant scan rate of 10° C./min until atemperature of at least 30° C. and preferably at least 50° C. above themelting point is reached.

The present invention relates to overmolded composite structures andprocesses to make them. The overmolded composite structure according tothe present invention comprises at least two components, i.e. a firstcomponent and a second component. The first component consists of acomposite structure having a surface, which surface has at least aportion made of a surface resin composition, and comprises a fibrousmaterial selected from non-woven structures, textiles, fibrous battingsand combinations thereof, said fibrous material being impregnated with amatrix resin composition.

The overmolded composite structure may comprise more than one firstcomponents, i.e. it may comprise more than one composite structures andmay comprise more than one second components.

The second component is adhered to the first component over at least aportion of the surface of said first component, the portion of thesurface being made of the surface resin composition described herein.The first component may be fully or partially encapsulated by the secondcomponent.

As used herein, the term “a fibrous material being impregnated with amatrix resin composition” means that the matrix resin compositionencapsulates and embeds the fibrous material so as to form aninterpenetrating network of fibrous material substantially surrounded bythe matrix resin composition. For purposes herein, the term “fiber”refers to a macroscopically homogeneous body having a high ratio oflength to width across its cross-sectional area perpendicular to itslength. The fiber cross section can be any shape, but is typicallyround. The fibrous material may be in any suitable form known to thoseskilled in the art and is preferably selected from non-woven structures,textiles, fibrous battings and combinations thereof. Non-wovenstructures can be selected from random fiber orientation or alignedfibrous structures. Examples of random fiber orientation include withoutlimitation chopped and continuous material which can be in the form of amat, a needled mat or a felt. Examples of aligned fibrous structuresinclude without limitation unidirectional fiber strands, bidirectionalstrands, multidirectional strands, multi-axial textiles. Textiles can beselected from woven forms, knits, braids and combinations thereof. Thefibrous material can be continuous or discontinuous in form.

Depending on the end-use application of the overmolded compositestructure and the required mechanical properties, more than one fibrousmaterials can be used, either by using several same fibrous materials ora combination of different fibrous materials, i.e. the first componentdescribed herein may comprise one or more fibrous materials. An exampleof a combination of different fibrous materials is a combinationcomprising a non-woven structure such as for example a planar random matwhich is placed as a central layer and one or more woven continuousfibrous materials that are placed as outside layers. Such a combinationallows an improvement of the processing and thereof of the homogeneityof the first component thus leading to improved mechanical properties.The fibrous material may be made of any suitable material or a mixtureof materials provided that the material or the mixture of materialswithstand the processing conditions used during impregnation by thematrix resin composition and the surface resin composition.

Preferably, the fibrous material comprises glass fibers, carbon fibers,aramid fibers, graphite fibers, metal fibers, ceramic fibers, naturalfibers or mixtures thereof; more preferably, the fibrous materialcomprises glass fibers, carbon fibers, aramid fibers, natural fibers ormixtures thereof; and still more preferably, the fibrous materialcomprises glass fibers, carbon fibers and aramid fibers or mixturemixtures thereof. By natural fiber, it is meant any of material of plantorigin or of animal origin. When used, the natural fibers are preferablyderived from vegetable sources such as for example from seed hair (e.g.cotton), stem plants (e.g. hemp, flax, bamboo; both bast and corefibers), leaf plants (e.g. sisal and abaca), agricultural fibers (e.g.,cereal straw, corn cobs, rice hulls and coconut hair) or lignocellulosicfiber (e.g. wood, wood fibers, wood flour, paper and wood-relatedmaterials). As mentioned above, more than one fibrous materials can beused. A combination of fibrous materials made of different fibers can beused such as for example a composite structure comprising one or morecentral layers made of glass fibers or natural fibers and one or moresurface layers made of carbon fibers or glass fibers. Preferably, thefibrous material is selected from woven structures, non-woven structuresor combinations thereof, wherein said structures are made of glassfibers and wherein the glass fibers are E-glass filaments with adiameter between 8 and 30 microns and preferably with a diameter between10 to 24 microns.

The fibrous material may further contain a thermoplastic material andthe materials described above, for example the fibrous material may bein the form of commingled or co-woven yarns or a fibrous materialimpregnated with a powder made of a thermoplastic material that issuited to subsequent processing into woven or non-woven forms, or amixture for use as a uni-directional material or a fibrous materialimpregnated with oligomers that will polymerize in situ duringimpregnation.

Preferably, the ratio between the fibrous material and the polymermaterials in the first component. i.e. the fibrous material incombination with the matrix resin composition and the surface resincomposition, is at least 30 volume percent fibrous material and morepreferably between 40 and 60 volume percent fibrous material, thepercentage being a volume-percentage based on the total volume of thefirst component.

The matrix resin composition of the first component is made of athermoplastic resin that is compatible with the surface resincomposition.

The surface resin composition is selected from polyamide compositionscomprising a blend of two or more fully aliphatic polyamides having amelting point of at least 250° C. Preferably the surface resincomposition is selected from polyamide compositions comprising a blendof poly(tetramethylene hexanediamide) (PA46) with one or more fullyaliphatic polyamides having a melting point of at least 250° C. Evenmore preferably, the surface resin composition is selected frompolyamide compositions comprising a blend of poly(tetramethylenehexanediamide) (PA46) with poly(hexamethylene hexanediamide) (PA66).

The matrix resin composition is selected from polyamide compositionscomprising one or more fully aliphatic polyamides having a melting pointof at least 250° C. Preferably, the matrix resin composition is selectedfrom polyamide compositions comprising a blend of two or more fullyaliphatic polyamides having a melting point of at least 250° C. Evenmore preferably, the matrix resin composition is selected from polyamidecompositions comprising a poly(tetramethylene hexanediamide) (PA46) orpoly(hexamethylene hexanediamide) (PA66) and mixtures or blends thereof.When the matrix resin composition and the surface resin composition areselected from polyamide compositions comprising a blend of two or morefully aliphatic polyamides having a melting point of at least 250° C.,the matrix resin composition and the surface resin composition may beidentical or different.

When the matrix resin composition and the surface resin composition aredifferent, it means that their respective blend of polyamides comprisesat least one different polyamide, or that their blend of polyamides arethe same polyamides but made of different ratios.

Preferably, the surface resin composition and the matrix resincomposition comprise a blend of two or more or more fully aliphaticpolyamides having a melting point of at least 250° C. in a weight ratiofrom about 1:99 to about 95:5, more preferably from about 15:85 to about85:15. Still more preferably surface resin composition and the matrixresin composition comprises a blend of two or more or more fullyaliphatic polyamides having a melting point of at least 250° C. in aweight ratio from about 20:80 to about 30:70.

The overmolding resin composition may be any polyamide resin, but ispreferably a fully aliphatic polyamide resin. It may be the same ordifferent from the surface resin composition and/or the matrix resincomposition, and may be a blend of polyamides or a single polyamideresin. In a preferred embodiment it is selected from polyamides having amelting point of at least 250° C.

Polyamides are condensation products of one or more dicarboxylic acidsand one or more diamines, and/or one or more aminocarboxylic acids,and/or ring-opening polymerization products of one or more cycliclactams.

The two or more fully aliphatic polyamides are formed from aliphatic andalicyclic monomers such as diamines, dicarboxylic acids, lactams,aminocarboxylic acids, and their reactive equivalents. A suitableaminocarboxylic acid is 11-aminododecanoic acid. Suitable lactamsinclude caprolactam and laurolactam. In the context of this invention,the term “fully aliphatic polyamide” also refers to copolymers derivedfrom two or more such monomers and blends of two or more fully aliphaticpolyamides. Linear, branched, and cyclic monomers may be used.

Carboxylic acid monomers comprised in the fully aliphatic polyamides arealiphatic carboxylic acids, such as for example adipic acid (C6),pimelic acid (C7), suberic acid (C8), azelaic acid (C9), sebacic acid(C10), dodecanedioic acid (C12) and tetradecanedioic acid (C14).Preferably, the aliphatic dicarboxylic acids of the fully aliphaticpolyamides are selected from adipic acid and dodecanedioic acid. Thefully aliphatic polyamides described herein comprise an aliphaticdiamine as previously described. Preferably, the one or more diaminemonomers of the two or more fully aliphatic polyamide copolymeraccording to the present invention are selected from tetramethylenediamine and hexamethylene diamine. Suitable examples of fully aliphaticpolyamides are poly(hexamethylene adipamide (also called polyamide 6,6;polyamide 66, PA66, or nylon 66), and poly(tetramethylene adipamide)(also called polyamide 4,6, polyamide 46, PA46, or nylon 46), and anycopolymers and combinations of the 2, or of either or both with otherpolyamides, provided that the copolymer has at least 250° C. meltingpoint. Suitable polyamides having a melting point of at least 250° C.,are polyamides selected from the group poly(hexamethylene hexanediamide)(PA 66), poly(ε-caprolactam/hexamethylene hexanediamide) (PA6/66),(PA6/66/610), poly(ε-caprolactam/hexamethylenehexanediamide/hexamethylene dodecanediamide) (PA6/66/612),poly(ε-caprolactam/hexamethylene hexanediamide/hexamethylenedecanediamide/hexamethylene dodecanediamide) (PA6/66/610/612),poly(2-methylpentamethylene hexanediamide/hexamethylene hexanediamide/)(PA D6/66), poly(tetramethylene hexanediamide) (PA46). Preferredexamples of fully aliphatic polyamides useful in the polyamidecomposition of the present invention are PA66 and PA46.

An embodiment of the current invention comprises a matrix resincomposition and a surface resin composition comprising a blend ofpoly(tetramethylene hexanediamide) (PA46) with one or more fullyaliphatic polyamides having a melting point of at least 250° C.

A preferred embodiment of the current invention comprise a matrix resincomposition comprising a blend of poly(tetramethylene hexanediamide)(PA46) with poly(hexamethylene hexanediamide) (PA66).

Another preferred embodiment of the current invention comprise a matrixresin composition comprising a blend of poly(tetramethylenehexanediamide) (PA46) with poly(hexamethylene hexanediamide) (PA66) in aratio of 50:50.

The overmolded composite structure comprises a second componentcomprising an overmolding resin composition as described above. Thesecond component is adhered to the first component described above overat least a portion of the surface of the first component.

The surface resin composition described herein and/or the matrix resincomposition and/or the overmolding resin composition may furthercomprise one or more impact modifiers, one or more heat stabilizers, oneor more oxidative stabilizers, one or more ultraviolet lightstabilizers, one or more flame retardant agents or mixtures thereof.

The surface resin composition described herein and/or the matrix resincomposition and/or the overmolding resin composition may furthercomprise one or more reinforcing agents such as glass fibers, glassflakes, carbon fibers, carbon nanotubes, mica, wollastonite, calciumcarbonate, talc, calcined clay, kaolin, magnesium sulfate, magnesiumsilicate, boron nitride, barium sulfate, titanium dioxide, sodiumaluminum carbonate, barium ferrite, and potassium titanate. Whenpresent, the one or more reinforcing agents are present in an amountfrom at or about 1 to at or about 60 wt-%, preferably from at or about 1to at or about 40 wt-%, or more preferably from at or about 1 to at orabout 35 wt-%, the weight percentages being based on the total weight ofthe surface resin composition or the matrix resin composition or theovermolding resin composition, as the case may be.

As mentioned above, the matrix resin composition and the surface resincomposition may be identical or different. With the aim of increasingthe impregnation rate of the fibrous material, the melt viscosity of thecompositions may be reduced and especially the melt viscosity of thematrix resin composition.

The surface resin composition described herein and/or the matrix resincomposition and/or the overmolding resin composition may furthercomprise modifiers and other ingredients, including, without limitation,flow enhancing additives, lubricants, antistatic agents, coloring agents(including dyes, pigments, carbon black, and the like), nucleatingagents, crystallization promoting agents and other processing aids knownin the polymer compounding art.

Fillers, modifiers and other ingredients described above may be presentin the composition in amounts and in forms well known in the art,including in the form of so-called nano-materials where at least one ofthe dimensions of the particles is in the range of 1 to 1000 nm.

Preferably, the surface resin compositions and the matrix resincompositions and the overmolding resin composition are melt-mixedblends, wherein all of the polymeric components are well-dispersedwithin each other and all of the non-polymeric ingredients arewell-dispersed in and bound by the polymer matrix, such that the blendforms a unified whole. Any melt-mixing method may be used to combine thepolymeric components and non-polymeric ingredients of the presentinvention. For example, the polymeric components and non-polymericingredients may be added to a melt mixer, such as, for example, a singleor twin-screw extruder; a blender; a single or twin-screw kneader; or aBanbury mixer, either all at once through a single step addition, or ina stepwise fashion, and then melt-mixed. When adding the polymericcomponents and non-polymeric ingredients in a stepwise fashion, part ofthe polymeric components and/or non-polymeric ingredients are firstadded and melt-mixed with the remaining polymeric components andnon-polymeric ingredients being subsequently added and furthermelt-mixed until a well-mixed composition is obtained.

The overmolded composite structure according to the present inventionmay be manufactured by a process comprising a step of overmolding thefirst component described above with the overmolding resin composition.By “overmolding”, it is meant that a second component comprising theovermolding resin composition described herein is molded or extrudedonto at least one portion of the surface of the first component, whichsurface is made of a surface resin composition.

The overmolding process includes that the second component is molded ina mold already containing the first component, the latter having beenmanufactured beforehand as described hereafter, so that the first andsecond components are adhered to each other over at least a portion ofthe surface of the first component. The first component is positioned ina mold having a cavity defining the outer surface of the finalovermolded composite structure. The overmolding resin composition may beovermolded on one side or on both sides of the first component and itmay fully or partially encapsulate the first component. After havingpositioned the first component in mold, the overmolding resincomposition is then introduced in a molten form. The first component andthe second component are adhered together by overmolding. The at leasttwo parts are preferably adhered together by injection or compressionmolding as an overmolding step, and more preferably by injectionmolding.

Depending on the end-use application, the first component according tothe present invention may have any shape. In a preferred embodiment, thefirst component according to the present invention is in the form of asheet structure. The first component may be flexible, in which case itcan be rolled.

The first component can be made by a process that comprises a step ofimpregnating the fibrous material with the matrix resin composition,wherein at least a portion of the surface of the first component, i.e.the composite structure, is made of the surface resin composition.Preferably, the fibrous material is impregnated with the matrix resin bythermopressing. During thermopressing, the fibrous material, the matrixresin composition and the surface resin composition undergo heat andpressure in order to allow the resin compositions to melt and penetratethrough the fibrous material and, therefore, to impregnate said fibrousmaterial.

Typically, thermopressing is made at a pressure between 2 and 100 barsand more preferably between 10 and 40 bars and a temperature which isabove the melting point of the matrix resin composition and the surfaceresin composition, preferably at least about 20° C. above the meltingpoint to enable a proper impregnation. Heating may be done by a varietyof means, including contact heating, radiant gas heating, infra redheating, convection or forced convection air heating, induction heating,microwave heating or combinations thereof.

The impregnation pressure can be applied by a static process or by acontinuous process (also known as dynamic process), a continuous processbeing preferred for reasons of speed. Examples of impregnation processesinclude without limitation vacuum molding, in-mold coating, cross-dieextrusion, pultrusion, wire coating type processes, lamination,stamping, diaphragm forming or press-molding, lamination beingpreferred. During lamination, heat and pressure are applied to thefibrous material, the matrix resin composition and the surface resincomposition through opposing pressured rollers or belts in a heatingzone, preferably followed by the continued application of pressure in acooling zone to finalize consolidation and cool the impregnated fibrousmaterial by pressurized means. Examples of lamination techniques includewithout limation calendering, flatbed lamination and double-belt presslamination. When lamination is used as the impregnating process,preferably a double-belt press is used for lamination.

Should the matrix resin composition and the surface resin composition bedifferent, the surface resin composition always faces the environment ofthe first component so as to be accessible when the overmolding resincomposition is applied onto the first component.

The matrix resin composition and the surface resin composition areapplied to the fibrous material by conventional means such as forexample powder coating, film lamination, extrusion coating or acombination of two or more thereof, provided that the surface resincomposition is applied on at least a portion of the surface of thecomposite structure, which surface is exposed to the environment of thefirst component.

During a powder coating process, a polymer powder which has beenobtained by conventional grinding methods is applied to the fibrousmaterial. The powder may be applied onto the fibrous material byscattering, sprinkling, spraying, thermal or flame spraying, orfluidized bed coating methods. Optionally, the powder coating processmay further comprise a step which consists in a post sintering step ofthe powder on the fibrous material. The matrix resin composition and thesurface resin composition are applied to the fibrous material such thatat least a portion of the surface of the first component is made of thesurface resin composition. Subsequently, thermopressing is performed onthe powder coated fibrous material, with an optional preheating of thepowder coated fibrous material outside of the pressurized zone.

During film lamination, one or more films made of the matrix resincomposition and one or more films made of the surface resin compositionwhich have been obtained by conventional extrusion methods known in theart such as for example blow film extrusion, cast film extrusion andcast sheet extrusion are applied to the fibrous material, e.g. bylayering. Subsequently, thermopressing is performed on the assemblycomprising the one or more films made of the matrix resin compositionand the one or more films made of the surface resin composition and theone or more fibrous materials. In the resulting first component, thefilms melt and penetrate around the fibrous material as a polymercontinuum surrounding the fibrous material.

During extrusion coating, pellets and/or granulates made of the matrixresin composition and pellets and/or granulates made of the surfaceresin composition are melted and extruded through one or more flat diesso as to form one or more melt curtains which are then applied onto thefibrous material by laying down the one or more melt curtains.Subsequently, thermopressing is performed on the assembly comprising thematrix resin composition, the surface resin composition and the one ormore fibrous materials.

While it is possible to preheat the first component at a temperatureclose to but below the melt temperature of the matrix resin compositionprior to the overmolding step so as to improve the adhesion between thesurface of the first component and the overmolding resin and then torapidly transfer the heated composite structure for overmolding; such astep can be improved or even eliminated by using the overmolding resincomposition and the surface resin composition. Due to the high adhesionand high bond strength between the overmolding resin and the surfaceresin composition of the overmolded composite structure according to thepresent invention, the need for a preheating step is strongly reduced oreven eliminated. Should a preheating step be used, the transfer time maynot be as critical as for conventional composite structures, meaningthat the transfer time may be increased thereby increasing theprocessing window and reducing molding equipment and automation costs.Such a preheating step may be done by a variety of means, includingcontact heating, radiant gas heating, infra red heating, convection orforced convection air heating, induction heating, microwave heating orcombinations thereof.

Depending on the end-use application, the first component may be shapedinto a desired geometry or configuration, or used in sheet form prior tothe step of overmolding the overmolding resin composition. The firstcomponent may be flexible, in which case it can be rolled.

The process for making a shaped first component further comprises a stepof shaping the first component, said step arising after the impregnatingstep. The step of shaping the first component may be done by compressionmolding, stamping or any technique using heat and/or pressure,compression molding and stamping being preferred. Preferably, pressureis applied by using a hydraulic molding press. During compressionmolding or stamping, the first component is preheated to a temperatureabove the melt temperature of the surface resin composition andpreferably above the melt temperature of the matrix resin composition byheated means and is transferred to a forming or shaping means such as amolding press containing a mold having a cavity of the shape of thefinal desired geometry whereby it is shaped into a desired configurationand is thereafter removed from the press or the mold after cooling to atemperature below the melt temperature of the surface resin compositionand preferably below the melt temperature of the matrix resincomposition. With the aim of further improving the adhesion between theovermolding resin and the surface resin composition, the surface of thefirst component may be a textured surface so as to increase the relativesurface available for overmolding, such textured surface may be obtainedduring the step of shaping by using a press or a mold having for exampleporosities or indentations on its surface.

Alternatively, a one step process comprising the steps of shaping andovermolding the first component in a single molding station may be used.This one step process avoids the step of compression molding or stampingthe first component in a mold or a press, avoids the optional preheatingstep and the transfer of the preheated first component to the moldingstation. During this one step process, the first component, i.e. thecomposite structure, is heated outside, adjacent to or within themolding station, to a temperature at which the first component isconformable or shapable during the overmolding step. In such a one stepprocess, the molding station comprises a mold having a cavity of theshape of the final desired geometry. The shape of the first component isthereby obtained during overmolding.

The overmolded composite structures according to the present inventionmay be used in a wide variety of applications such as for example ascomponents for automobiles, trucks, commercial airplanes, aerospace,rail, household appliances, computer hardware, hand held devices,recreation and sports, structural component for machines, structuralcomponents for buildings, structural components for photovoltaicequipments or structural components for mechanical devices.

Examples of automotive applications include without limitation seatingcomponents and seating frames, engine cover brackets, engine cradles,suspension arms and cradles, spare tire wells, chassis reinforcement,floor pans, front-end modules, steering column frames, instrumentpanels, door systems, body panels (such as horizontal body panels anddoor panels), tailgates, hardtop frame structures, convertible top framestructures, roofing structures, engine covers, housings for transmissionand power delivery components, oil pans, airbag housing canisters,automotive interior impact structures, engine support brackets, crosscar beams, bumper beams, pedestrian safety beams, firewalls, rear parcelshelves, cross vehicle bulkheads, pressure vessels such as refrigerantbottles and fire extinguishers and truck compressed air brake systemvessels, hybrid internal combustion/electric or electric vehicle batterytrays, automotive suspension wishbone and control arms, suspensionstabilizer links, leaf springs, vehicle wheels, recreational vehicle andmotorcycle swing arms, fenders, roofing frames and tank flaps.

Examples of household appliances include without limitation washers,dryers, refrigerators, air conditioning and heating. Examples ofrecreation and sports include without limitation inline-skatecomponents, baseball bats, hockey sticks, ski and snowboard bindings,rucksack backs and frames, and bicycle frames. Examples of structuralcomponents for machines include electrical/electronic parts such as forexample housings for hand held electronic devices, computers.

Examples Materials

The materials below are comprised in the compositions used in theExamples and Comparative Examples.

Polyamide 1 (PA1 in Tables): an aliphatic polyamide, poly(tetramethylenehexanediamide). This polyamide is called PA46 and is commerciallyavailable, for example, from DSM corporation. PA1 has a melting point ofabout 275° C. to about 290° C.

Polyamide 2 (PA2 in Tables): an aliphatic polyamide made of adipic acidand 1,6-hexamethylenediamine with a weight average molecular weight ofaround 32000 Daltons. This polyamide is called PA6,6 and is commerciallyavailable, for example, from E. I. du Pont de Nemours and Company. PA2has a melting point of about 260° C. to about 265° C.

Overmolding resin: a composition comprising a polyamide (PA2) made ofadipic acid and 1,6-hexamethylenediamine, 50 percent glass fibers byweight of the total composition. The resin is commercially availablefrom E. I. du Pont de Nemours and Company.

Preparation of Films

The resin compositions used in the Examples (abbreviated as “E” inTables 1 to 3), and Comparative Examples (abbreviated as “C” in Tables 1to 3) were prepared by melting or melt-blending the ingredients in atwin-screw extruder at about 300° C. in the case of matrix resin andsurface resin compositions of E1 to E3, and C1, C3, and C5, and thesurface resin composition of E4 and C7, or at about 280° C. in the caseof the matrix resin compositions of E4, C2, C4, and C6 to C8, and thesurface resin compositions of C2, C4, C6, and C8. The compositionsexited the extruder through an adaptor and a film die at the respectivetemperatures, and then were cast onto a casting drum at about 100° C.into about 125 micron thick film in the case of the matrix resin and thesurface resin compositions of E1 to E3, and C1, C3, and C5, and thesurface resin compositions of E4 and C7, and into about 250 micron thickfilm in the case of the matrix resin and the surface resin compositionsof C2, C4, and C6, and the surface resin compositions of C8, and intoabout 102 micron thick film in the case of the matrix resin compositionsof E4, C7, and C8. The thickness of the films was controlled by the rateof drawing.

Preparation of the Composite Structures in Tables 1 and 2

Preparation of the composite structures E1, C1, and C2 in Table 1 andthe composite structures used to make the overmolded compositestructures E2, E3, and C3 to C6 in Table 2 was accomplished bylaminating multiple layers of film of compositions shown in Tables 1 and2, and woven continuous glass fiber textile (prepared from E-glassfibers having a diameter of 17 microns, sized with 0.4% of asilane-based sizing agent and a nominal roving tex of 1200 g/km thathave been woven into a 2/2 twill (balanced weave) with an areal weightof 600 g/m²) in the following sequence for E1 to E3, and C1, C3, and C5:4 layers of film of surface resin composition, one layer of wovencontinuous glass fiber textile, 4 layers of film of matrix resincomposition, one layer of woven continuous glass fiber textile, fourlayers of film of matrix resin composition, one layer of wovencontinuous glass fiber textile, and four layers of film of surface resincomposition; and in the following sequence for C2, C4, and C6: twolayers of film of surface resin composition, one layer of wovencontinuous glass fiber textile, two layers of film of matrix resincomposition, one layer of woven continuous glass fiber textile, twolayers of film of matrix resin composition, one layer of wovencontinuous glass fiber textile, and two layers of film of surface resincomposition.

The composite structures of tables 1 and 2 were compression molded by aDake Press (Grand Haven, Mich.) Model 44-225, Pressure range 0-25K, withan 8 inch platten. A 6×6″ specimen of film and glass textile layers asdescribed above was placed in the mold and heated to a temperature ofabout 320° C., held at the temperature for 2 minutes without pressure,then pressed at the 320° C. temperature with the following pressures:about 4 bar for about 2 minutes, then with about 12 bar for about 2additional minutes, and then with about 20 bar for about 2 additionalminutes; they were subsequently cooled to ambient temperature. Thethusly formed composite structures had a thickness of about 1.6 mm, andglass fiber content in the range of 55 to 60 percent of the total weightof the composite structure.

Preparation of the Composite Structures in Table 3

The composite structures used to make the overmolded compositestructures E4, C7, and C8 (of Table 3) were prepared by first making alaminate by stacking eight layers having a thickness of about 102microns and made of PA2 and three layers of woven continuous glass fibertextile (E-glass fibers having a diameter of 17 microns, 0.4% of asilane-based sizing and a nominal roving tex of 1200 g/km that have beenwoven into a 2/2 twill (balanced weave) with an areal weight of 600g/m²) in the following sequence: two layers made of PA2, one layer ofwoven continuous glass fiber textile, two layers of PA2, one layer ofwoven continuous glass fiber textile, two layers of PA2, one layer ofwoven continuous glass fiber textile and two layers of PA2.

The laminates were prepared using an isobaric double press machine withcounter rotating steel belts, both supplied by Held GmbH. The differentfilms enterered the machine from unwinders in the previously definedstacking sequence. The heating zones were about 2000 mm long and thecooling zones were about 1000 mm long. Heating and cooling weremaintained without release of pressure. The laminates were prepared withthe following conditions: a lamination rate of 1 m/min, a maximummachine temperature of 360° C. and laminate pressure of 40 bar. Theso-obtained laminates had an overall thickness of about 1.5 mm.

Two layers of films of about 125 micrometers in the case of E4 and C7and 1 layer of film of about 250 micrometers in the case of C8, made ofthe respective surface polyamide resin compositions of E4, C7, and C8 asdescribed in Table 3 were applied to a 6×6″ specimen of the abovedescribed laminate, forming the composite structure. The compositestructures were compression molded by a Dake Press (Grand Haven, Mich.)Model 44-225 (pressure range 0-25K) with an 8 inch platten at atemperature of about 320° C., held at the temperature for 2 minuteswithout pressure, then pressed at the 320° C. temperature with thefollowing pressures: about 4 bar for about 2 minutes, then with about 23bar for about 2 additional minutes, and then with about 46 bar for about2 additional minutes; they were subsequently cooled to ambienttemperature. The composite structures used to make overmolded compositestructures E4, C7, and C8 and comprising a surface made of the surfacepolyamide resin compositions as described in Table 3, the matrix resincompositions PA2 and the fibrous material had an overall thickness ofabout 1.6 mm.

Preparation of the Overmolded Composite Structures in Tables 2 and 3

The overmolded composite structures listed in Tables 2 and 3 were madeby over injection molding about 1.8 mm of the overmolding resincomposition onto the composite structures obtained as described above.

The composite structures for E2 to E4, and C3 to C8, were cut into 5×5″(about 127 mm×127 mm) specimens and placed into a heating chamber for 3min at 210° C. or for 3 min at 170° C. as shown in Tables 2 and 3. Thenthey were quickly transferred with a robot arm into a mold cavity of anEngel vertical press where the second component was injection moldedover the first component by an Engel molding machine. The transfer timefrom leaving the heating chamber to contact with the overmolding resinwas 9 sec. The mold cavity of the Engel molding machine was oil heatedat 120° C. and the injection machine was set at 280° C. during injectionof the overmolding resin onto the composite structures.

Flexural Strength of Composite Structures E1, C1, and C2 in Table 1

The composite structures E1, C1, and C2 in Table 1 were cut into ½″(about 12.7 mm) by 2.5″ (about 64 mm) long test specimens (bars) using aMK-377 Tile Saw with a diamond edged blade and water as a lubricant.Flexural Strength was tested on the test specimens via a 3-point bendtest. The apparatus and geometry were according to ISO method 178,bending the specimen with a 2.0″ support width with the loading edge atthe center of the span. The tests were conducted with 1 KN load at 2mm/min until fracture. The results are shown in Table 1, 428, 408, and332 MPa for composite structures E1, C1, and C2 respectively,demonstrating the superior flexural strength of a composite structuremade of a blend of aliphatic polyamides selected from a group ofpolyamides of melting points higher than 250° C., when compared to acomposite structure made of a single polyamide from the same group ofpolyamides.

Flexural Strength of Overmolded Composite Structures E2, E3, and C3 toC6 in Table 2

The overmolded composite structures E2, E3, and C3 to C6 in Table 2 werecut into ½″ (about 12.7 mm) by 2.5″ (about 64 mm) long test specimens(bars) using a MK-377 Tile Saw with a diamond edged blade and water as alubricant. Some specimens delaminated on cutting, as shown in Table 2.Flexural Strength was tested on the remaining test specimens via a3-point bend test. The apparatus and geometry were according to ISOmethod 178, bending the specimen with a 2.0″ support width with theloading edge at the center of the span. The tests were conducted with 1KN load at 2 mm/min until fracture. The results are shown in Table 2.The results in Table 2 demonstrate the superior flexural strength of theovermolded composite structure made of a composite structure made of ablend of aliphatic polyamides selected from a group of polyamides ofmelting points higher than 250° C., when compared to the overmoldedcomposite structure made of a composite structure made of a singlepolyamide from the same group of polyamides. The results in Table 2 arealso indicative of the bonding strength between the 2 components of theovermolded composite structure.

Bond Strength of Overmolded Composite Structures E4, C7, and C8 of Table3

When composite structures E4, C7, and C8 were over-injection molded withthe overmolding resin composition comprising PA2 and 50 weight percentof glass fibers (percentage of the total composition of the overmoldingresin) as seen in Table 3, the bond strengths were respectively 61, 20,and 38 MPa, demonstrating the superior bond strength between a first andsecond components of overmolded composite structures wherein the firstcomponent comprises a surface resin composition made of a blend of 2 ormore polyamides selected from group of aliphatic polyamides of meltingpoints higher than 250° C., than that of overmolded composite structureswherein the first component comprises a surface resin composition madeof a single aliphatic polyamide from the same group.

The composite structures E4, C7, and C8 comprising a surface made of thesurface resin compositions listed in Table 3, the matrix resincompositions listed in Table 3 (PA2) and the fibrous material describedabove, were over-injection molded with the overmolding resin (Table 3)as described above, by first preheating the 5×5″ (about 127 mm×127 mm)specimens for 3 min at 210° C. The 5×5″ specimens of the overmoldedcomposite structures E4, C7, and C8, were cut into ½″ (about 12.7 mm)×3″(about 76 mm) test specimens, and were notched by cutting the secondcomponent (overmolded resin) up to the interface of the second componentand the first component (the composite structure). The notch was madethrough the width of the second component at about the middle(lengthwise) of the test specimen. The bond strength between the 2components of the overmolded composite structure was measured on thenotched test specimens via a 3 point bend method, modified ISO-178. Theapparatus and geometry were according to ISO method 178, bending thespecimen with a 2.0″ (about 51 mm) support width with the loading edgeat the center of the span. The over-molded second component of thespecimen was on the tensile side (outer span) resting on the two sidesupports (at 2″ (about 51 mm) apart), while indenting with the singlesupport (the load) on the compression side (inner span) on the compositestructure of the specimen. In this test geometry, the notch in thespecimens was down (tensile side). The notch was placed ¼″ off center(¼″ away from the load). The tests were conducted at 2 mm/min with a 1KN load. The test was run until a separation or fracture between the twocomponents of the specimen (delamination) was seen. The stress at thatpoint was recorded.

TABLE 1 E1 C1 C2 Matrix Resin Composition PA1 50 100 PA2 50 100 SurfaceResin Composition PA1 50 100 PA2 50 100 ISO-178 3 Point Flex FlexuralStrength at Break (Mpa) 423 408 332

TABLE 2 E2 C3 C4 E3 C5 C6 Matrix Resin Composition PA1 50 100 50 100 PA250 100 50 100 Surface Resin Composition PA1 50 100 50 100 PA2 50 100 50100 Overmolding resin PA2 + 50% PA2 + 50% PA2 + 50% PA2 + 50% PA2 + 50%PA2 + 50% glass glass glass glass glass glass fibers fibers fibersfibers fibers fibers Pre-heat temperature 170  170 170 210  210 210 ofthe Composite structure (° C.) Number of specimens 0 out of 8 7 out of 80 out of 8 0 out of 8 1 out of 8 0 out of 8 delaminated on cuttingISO-178 3 Point Flex Flexural Strength at 265  188 228 298  186 258Break (Mpa), composite structure down

TABLE 3 E4 C7 C8 Matrix Resin Composition PA1 PA2 100 100 100 SurfaceResin Composition PA1 50 100 PA2 50 100 Overmolding resin PA2 + 50%PA2 + 50% PA2 + 50% glass fibers glass fibers glass fibers Pre-heattemperature of the 210 210 210 Composite structure (° C.) ISO-178 3Point Flex Flexural Strength (Mpa), 61 20 38 Notched overmolded resindown

1. An overmolded composite structure comprising: i) a first componenthaving a surface, which surface has at least a portion made of a surfaceresin composition, and comprising a fibrous material selected from thegroup consisting of non-woven structures, textiles, fibrous battings andcombinations thereof, said fibrous material being impregnated with amatrix resin composition, ii) a second component comprising anovermolding resin composition, wherein said second component is adheredto said first component over at least a portion of the surface of saidfirst component, and wherein the surface resin composition is selectedfrom polyamide compositions comprising a blend of two or more fullyaliphatic polyamides having a melting point of at least 250° C. andwherein the matrix resin composition is selected from polyamidecompositions comprising a one or more fully aliphatic polyamides havinga melting point of at least 250° C.
 2. The overmolded compositestructure of claim 1 wherein the surface resin composition is selectedfrom polyamide compositions comprising a blend of poly(tetramethylenehexanediamide) (PA46) with one or more fully aliphatic polyamides havinga melting point of at least 250° C.
 3. The overmolded compositestructure of claim 1 wherein the surface resin composition and thematrix resin composition are selected from polyamide compositionscomprising a blend of poly(tetramethylene hexanediamide) (PA46) withpoly(hexamethylene hexanediamide) (PA66).
 4. The overmolded compositestructure according to claim 1 wherein the overmolding resin compositionis selected from polyamide compositions comprising polyamides or blendsof polyamides having a melting point of at least 250° C.
 5. Theovermolded composite structure according to claim 1 wherein the fibrousmaterial is made of glass fibers, carbon fibers, aramid fibers, naturalfibers or mixtures thereof.
 6. The overmolded composite structureaccording to claim 1 wherein the fibrous material is made of glassfibers.
 7. The composite structure according to claim 1 wherein thefibrous material is from 30 volume percent to 60 volume percent of thecomposite structure.
 8. The composite structure according to claim 1further comprising one or more additives selected from the groupconsisting of heat stablizers, oxidative stabilizers, reinforcing agentsand flame retardants or combination thereof.
 9. The composite structureaccording to claim 1 wherein the two or more fully aliphatic polyamidesare selected from the group consisting of PA 66, PA6/66, PA6/66/610,PA6/66/612, PA6/66/610/612, PA D6/66, PA46.
 10. The overmolded compositestructure according to claim 1 wherein the weight ratio of the two ormore polyamides of the matrix polyamide composition and the surfaceresin composition is between from about 1:99 to about 95:5
 11. Theovermolded composite structure according to claim 1 wherein the weightratio of the one or more polyamides of the matrix polyamide compositionand of the surface resin composition is from about 40:60 to about 60:40.12. The overmolded composite structure according to claim 1 in the formof a component for automobiles, trucks, commercial airplanes, aerospace,rail, household appliances, computer hardware, hand held devices,recreation and sports, structural component for machines, structuralcomponents for buildings, structural components for photovoltaicequipments or structural components for mechanical devices.
 13. Aprocess for making an overmolded composite structure of claim 12comprising a step of overmolding a second component comprising anovermolding resin composition on a first component, wherein the firstcomponent comprises a fibrous material and has a surface, said surfacehaving at least a portion made of a surface resin composition, and saidfibrous material being selected from non-woven structures, textiles,fibrous battings and combinations thereof and said fibrous materialbeing impregnated with a matrix resin composition, said second componentbeing adhered to said first component over at least a portion of thesurface of said first component, wherein the surface resin compositionis selected from polyamide compositions comprising a blend of two ormore fully aliphatic polyamides having a melting point of at least 250°C. and wherein the matrix resin composition is selected from polyamidecompositions comprising a one or more fully aliphatic polyamides havinga melting point of at least 250° C.
 14. The process of claim 13 whereinthe surface resin composition is selected from polyamide compositionscomprising a blend of poly(tetramethylene hexanediamide) (PA46) with oneor more fully aliphatic polyamides having a melting point of at least250° C.
 15. The process of claim 13 wherein the surface resincomposition and the matrix resin composition are selected from polyamidecompositions comprising a blend of poly(tetramethylene hexanediamide)(PA46) with poly(hexamethylene hexanediamide) (PA66).
 16. The processaccording to claim 13, further comprising a step of shaping the firstcomponent, said step of shaping arising after the step of impregnatingbut before the step of overmolding.
 17. The process according to claim13 wherein the first component is heated before the step of overmoldingto soften and partially melt a surface which will form an interface withthe overmolding resin composition.
 18. The process according to claim 13wherein the first component is not heated before the step ofovermolding.